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Abstract:

An adhesive of the present invention is used for polarizing plate to
provide a transparent protective film on at least one side of a polarizer
and comprises a resin solution comprising a polyvinyl alcohol-based
resin, a crosslinking agent and a leveling agent containing an acetylene
skeleton-containing compound, wherein 0.01 to 10 parts by weight of the
leveling agent is added to 100 parts by weight of the polyvinyl
alcohol-based resin. The adhesive for polarizing plate can provide a
satisfactory wettability when applied to transparent protective films and
allows the production of polarizing plates to have water resistance at
high temperature and satisfactory optical properties.

Claims:

1. An adhesive for polarizing plate used for providing a transparent
protective film on at least one side of a polarizer, comprising:a resin
solution comprising a polyvinyl alcohol-based resin, a crosslinking agent
and a leveling agent containing an acetylene skeleton-containing
compound, wherein 0.01 to 10 parts by weight of the leveling agent is
added to 100 parts by weight of the polyvinyl alcohol-based resin.

2. The adhesive for polarizing plate according to claim 1, wherein the
leveling agent is an aqueous dispersion or aqueous solution containing
the acetylene skeleton-containing compound.

4. The adhesive for polarizing plate according to claim 1, wherein the
acetylene skeleton-containing compound is an ethylene oxide and/or a
propylene oxide adduct of acetylene glycol.

5. The adhesive for polarizing plate according to claim 1, wherein the
polyvinyl alcohol-based resin is a polyvinyl alcohol-based resin having
an acetoacetyl group.

6. The adhesive for polarizing plate according to claim 1, wherein the
crosslinking agent contains a methylol group-containing compound.

7. The adhesive for polarizing plate according to claim 1, wherein an
amount of the crosslinking agent is of 1 to 60 parts by weight based on
100 parts by weight of the polyvinyl alcohol-based resin.

8. A polarizing plate, comprising:a polarizer; anda transparent protective
film provided on at least one side of the polarizer with an adhesive
layer interposed therebetween, whereinthe adhesive layer is formed of the
adhesive for polarizing plate according to claim 1.

9. The polarizing plate according to claim 8, wherein the adhesive layer
has a thickness of 10 nm to 300 nm.

10. A method for manufacturing a polarizing plate comprising a polarizer
and a transparent protective film provided on at least one side of the
polarizer with an adhesive layer interposed therebetween, comprising the
steps of:preparing the adhesive for polarizing plate according to claim
1;applying the adhesive for polarizing plate to the transparent
protective film to form the adhesive layer; andlaminating the polarizer
to the adhesive layer-carrying transparent protective film through the
adhesive layer.

11. A method for manufacturing a polarizing plate comprising a polarizer
and a transparent protective film provided on at least one side of the
polarizer with an adhesive layer interposed therebetween, comprising the
steps of:preparing the adhesive for polarizing plate according to claim
1;applying the adhesive for polarizing plate to the transparent
protective film and then drying the adhesive to form the adhesive layer
on the transparent protective film; andlaminating the polarizer to the
adhesive layer-carrying transparent protective film through the adhesive
layer.

12. An optical film, comprising a laminate including at least one piece of
the polarizing plate according to claim 8.

13. An image display, comprising the polarizing plate according to claim
8.

14. An image display, comprising the optical film according to claim 12.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to an adhesive for polarizing plate.
The present invention further relates to a polarizing plate and
manufacturing method thereof using the adhesive for polarizing plate. The
polarizing plate alone or an optical film obtained by laminating the
polarizing plate can constitute an image display such as a liquid crystal
display, an organic EL display or PDP.

[0003]2. Description of the Related Art

[0004]In the liquid crystal displays, for example, it is indispensable to
dispose polarizers on both sides of a glass substrate providing a surface
of a liquid crystal panel according to an image formation scheme adopted
in the display. A polarizer is generally obtained in a procedure in which
a polyvinyl alcohol-based film is dyed with a dichroic material such as
iodine, thereafter, the film is crosslinked with a crosslinking agent and
then, mono-axially stretched to thereby form a film. Since the polarizer
is manufactured by stretching, it is easy to shrink. Since a polyvinyl
alcohol-based film comprises a hydrophilic polymer, the film is very
easily deformed especially in a humidified condition. Since the film
itself is weak in mechanical strength, there has been a problem that the
film is torn. Hence, adopted is a reinforced polarizing plate
manufactured in a procedure in which a transparent protective film or
transparent protective films each made from triacetyl cellulose or the
like are adhered to on one side or both sides of a polarizer. The
polarizing plate is manufactured by adhere the transparent protective
film onto a polarizer using an adhesive.

[0005]In recent years, the range of uses of liquid crystal displays has
been increased and extended to cover from portable terminals to large
screen home TVs, and their standards have been defined for each
application. In particular, portable terminal applications, which must be
portable for users, strongly demand durability. For example, polarizing
plates are required to have water resistance to such an extent that their
properties and form will not change even under humidified conditions,
further humidified conditions at high temperature such as conditions
causing dew condensation.

[0006]As mentioned above, a polarizer may be reinforced in strength with a
transparent protective film to form a polarizing plate before use. As an
adhesive for polarizing plate used in adhesion of the polarizer and the
transparent protective film to each other, an aqueous type adhesive is
conventionally preferable and, for example, a polyvinyl alcohol-based
adhesive obtained by mixing a crosslinking agent into a polyvinyl alcohol
aqueous solution has been employed. A polyvinyl alcohol-based adhesive
may cause peeling at the interface between a polarizer and a transparent
protective film in a humidified environment. This is considered because a
polyvinyl alcohol-based resin, which is a main component of the adhesive,
is a water-soluble polymer and a possibility of dissolution of an
adhesive occurs in a situation of dewing. In order to cope with the
problem, a proposal has been offered of an adhesive for polarizing plate
containing a polyvinyl alcohol-based resin having an acetoacetyl group,
and a crosslinking agent (see JP-A No.7-198945).

[0007]On the other hand, when a polarizer and a transparent protective
film are laminated together with the aqueous polyvinyl alcohol-based
adhesive interposed therebetween in the process of preparing a polarizing
plate, it is desired to improve the wettability of the transparent
protective film by the adhesive. For example, therefore, it is proposed
that the transparent protective film should be subjected to activation
treatment such as corona or plasma treatment (see JP-A No. 2006-178191).
In some cases, however, even after the transparent protective film is
subjected to activation treatment, the activation is insufficient so that
sufficient wettability cannot be obtained, depending on the type of the
transparent protective film. In order to improve wettability, it is also
proposed that an additive such as a fluoro surfactant or any other
surfactant, a specific acrylic resin, or a silicone leveling agent or any
other leveling agent should be added to the adhesive. However, mixing the
additive into the adhesive can undesirably reduce the adhesion
(particularly water-resistant adhesion) or lead to the production of
polarizing plates with degraded optical properties.

[0008]The polarizing plate may be manufactured by a method (precoating
method) including the steps of applying the aqueous polyvinyl
alcohol-based adhesive to a transparent protective film and then
laminating a polarizer to the transparent protective film after or
without drying or by another method (simultaneous coating method)
including the step of laminating a transparent protective film to a
polarizer, while interposing the adhesive between them by coating. Since
wettability is required to be good in the precoating method, however,
polarizing plates obtained by the precoating method have a problem in
which they can suffer from visible unevenness.

SUMMARY OF THE INVENTION

[0009]An object of the present invention is to provide an adhesive for
polarizing plate that is capable of providing a satisfactory wettability
when applied to transparent protective films and allows the production of
polarizing plates to have water resistance at high temperature and
satisfactory optical properties.

[0010]It is another object of the present invention to provide a
polarizing plate using the adhesive for polarizing plate and a
manufacturing method thereof. It is yet another object of the present
invention to provide an optical film laminating the polarizing plate,
further another object of the present invention to provide an image
display such as a liquid crystal display using the polarizing plate or
the optical film.

[0011]The inventors have conducted serious studies in order to solve the
above tasks with findings that the objects can be achieved with an
adhesive for polarizing plate shown below, having led to completion of
the present invention.

[0012]The present invention relates to an adhesive for polarizing plate
used for providing a transparent protective film on at least one side of
a polarizer, comprising:

[0013]a resin solution comprising a polyvinyl alcohol-based resin, a
crosslinking agent and a leveling agent containing an acetylene
skeleton-containing compound, wherein 0.01 to 10 parts by weight of the
leveling agent is added to 100 parts by weight of the polyvinyl
alcohol-based resin.

[0014]In the adhesive for polarizing plate, the leveling agent is
preferably an aqueous dispersion or aqueous solution containing the
acetylene skeleton-containing compound. And the aqueous dispersion
preferably contains alkylene glycol.

[0015]In the adhesive for polarizing plate, the acetylene
skeleton-containing compound is preferably an ethylene oxide and/or a
propylene oxide adduct of acetylene glycol.

[0016]It is favorable when the polyvinyl alcohol-based resin used in the
adhesive for polarizing plate is a polyvinyl alcohol-based resin having
an acetoacetyl group.

[0018]In the adhesive for polarizing plate, an amount of the crosslinking
agent is preferably of 1 to 60 parts by weight based on 100 parts by
weight of the polyvinyl alcohol-based resin.

[0019]The present invention also relates to a polarizing plate,
comprising: a polarizer; and a transparent protective film provided on at
least one side of the polarizer with an adhesive layer interposed
therebetween, wherein the adhesive layer is formed of the adhesive for
polarizing plate.

[0020]In the polarizing plate, the adhesive layer preferably has a
thickness of 10 nm to 300 nm.

[0021]The present invention also relates to a method for manufacturing a
polarizing plate comprising a polarizer and a transparent protective film
provided on at least one side of the polarizer with an adhesive layer
interposed therebetween, comprising the steps of: preparing the
above-described adhesive for polarizing plate; applying the adhesive for
polarizing plate to the transparent protective film to form the adhesive
layer; and laminating the polarizer to the adhesive layer-carrying
transparent protective film through the adhesive layer.

[0022]The present invention also relates to a method for manufacturing a
polarizing plate comprising a polarizer and a transparent protective film
provided on at least one side of the polarizer with an adhesive layer
interposed therebetween, comprising the steps of: preparing the
above-described adhesive for polarizing plate; applying the adhesive for
polarizing plate to the transparent protective film and then drying the
adhesive to form the adhesive layer on the transparent protective film;
and laminating the polarizer to the adhesive layer-carrying transparent
protective film through the adhesive layer.

[0023]The present invention also relates to an optical film, comprising a
laminate including at least one piece of the above-described polarizing
plate.

[0024]The present invention also relates to an image display, comprising
the above-described polarizing plate or the above-described optical film.

[0025]The adhesive for polarizing plate of the present invention contains
not only a polyvinyl alcohol-based resin and a crosslinking agent but
also a leveling agent containing an acetylene skeleton-containing
compound. The leveling agent can act to achieve satisfactory wettability,
when the adhesive is applied to various transparent protective films.
Therefore, with the adhesive for polarizing plate of the present
invention, polarizing plates produced even by precoating methods can be
prevented from suffering from unevenness. Thus, the yield of
manufacturing polarizing plates can be improved so that the polarizing
plate productivity can be improved. Precoating methods for manufacturing
polarizing plates include a method including the steps of applying the
adhesive for polarizing plate to a transparent protective film,
subjecting the adhesive to a drying process to form a dried
pressure-sensitive adhesive layer, and then laminating the
pressure-sensitive adhesive layer to a polarizer and a method including
the steps of applying the adhesive to a transparent protective film and
then laminating a polarizer to the transparent protective film without
performing a drying process. The adhesive for polarizing plate of the
present invention can achieve satisfactory wettability in both methods
and is highly effective in the former method in which wettability is
particularly required.

[0026]The adhesive for polarizing plate of the present invention includes
a leveling agent containing an acetylene skeleton-containing compound.
The use of the specified amount of the leveling agent can ensure the
wettability and allows the production of polarizing plates exhibiting a
satisfactory adhesion even at high temperature and high humidity and
exhibiting a high level of water-resistant adhesion at high temperature.
The resulting polarizing plate can have satisfactory optical properties,
just like leveling agent-free polarizing plates.

BRIEF DESCRIPTION OF THE DRAWING

[0027]FIG. 1 shows a case where unevenness in a polarizing plate obtained
in an example was evaluated as "x".

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028]The adhesive for polarizing plate of the present invention is a
resin solution including a polyvinyl alcohol-based resin, a crosslinking
agent and a leveling agent containing an acetylene skeleton-containing
compound.

[0029]The polyvinyl alcohol-based resin may be a polyvinyl alcohol resin
or a polyvinyl alcohol-based resin having an acetoacetyl group. The
polyvinyl alcohol-based resin having an acetoacetyl group can form a
highly reactive functional group-containing polyvinyl alcohol-based
adhesive and thus is preferred because it can increase the durability of
the polarizing plate. Conventionally, when leveling agents are used in
adhesive for polarizing plates including an acetoacetyl group-containing
polyvinyl alcohol-based resin, reduction in water resistance or
degradation in optical properties is frequently observed. In contrast,
the use of the adhesive for polarizing plate of the present invention can
prevent reduction in water resistance or degradation in optical
properties, even when it includes an acetoacetyl group-containing
polyvinyl alcohol-based resin, because it also includes a leveling agent
containing the acetylene skeleton-containing compound.

[0030]Examples of polyvinyl alcohol-based resin include: a polyvinyl
alcohol obtained by saponifying a polyvinyl acetate; a derivative
thereof; a saponified copolymer of vinyl acetate and a monomer
copolymerizable therewith; and polyvinyl alcohols modified by
acetalization, urethanization, etherification, grafting, phosphate
esterification and the like. Examples of the monomers include,
unsaturated carboxylic acids such as maleic anhydride, fumaric acid,
crotonic acid, itaconic acid and (meth) acrylic acid, and esters thereof;
α-olefins such as ethylene and propylene; (meth)allylsulfonic acid
or sodium salt thereof, (meth)allylsulfonate; sodium sulfonate (monoalkyl
maleate), sodium disulfonate (alkyl maleate); N-methylolacrylamide; an
alkai salt of acrylamide alkylsulfonate; N-vinylpyrrolidone, a derivative
of N-vinylpyrrolidone and the like. The polyvinyl alcohol-based resins
can be either used alone or in combination of two kinds or more.

[0031]While no specific limitation is imposed on a polyvinyl alcohol-based
resin, an average degree of polymerization is from about 100 to about
5000, preferably from 1000 to 4000 and an average degree of
saponification is from about 85 to about 100 mol %, preferably from 90 to
100 mol % in consideration of adherence.

[0032]A polyvinyl alcohol-based resin having an acetoacetyl group is
obtained by reacting a polyvinyl alcohol-based resin and diketene to each
other with a known method. Examples of known methods include: a method in
which a polyvinyl alcohol-based resin is dispersed into a solvent such as
acetic acid, to which diketene is added and a method in which a polyvinyl
alcohol-based resin is previously dissolved into a solvent such as
dimethylformamide or dioxane, to which diketene is added. Another example
is a method in which diketene gas or diketene liquid is brought into
direct contact with a polyvinyl alcohol.

[0033]No specific limitation is imposed on a degree of modification by an
acetoacetyl group in a polyvinyl alcohol-based resin having an
acetoacetyl group or groups as far as the degree of modification is 0.1
mol % or more. If the degree of modification is less than 0.1 mol %,
water resistance of an adhesive layer is insufficient, which is improper.
A degree of modification by an acetoacetyl group is preferably from about
0.1 to about 40 mol %, more preferably from 2 to 7 mol %. If a degree of
modification by an acetoacetyl group exceeds 40 mol %, reaction sites
with a crosslinking agent is fewer to thereby reduce an effect of
improvement on moisture resistance and heat resistance. The degree of
modification by an acetoacetyl group is a value determined by NMR.

[0034]Any of crosslinking agents that have been used in a polyvinyl
alcohol-based adhesive can be used as a crosslinking agent in the present
invention without a specific limitation thereon. A crosslinking agent
that can be used is a compound having at least two functional groups
having reactivity with a polyvinyl alcohol-based resin. Examples thereof
include: alkylene diamines having an alkylene group and two amino groups
such as ethylene diamine, triethylene diamine and hexamethylene diamine;
isocyanates such as tolylene diisocyanate, hydrogenated tolylene
diisocyanate, trimethylolpropane tolylene diisocyanate adduct,
triphenylmethane triisocyanate,
methylenebis(4-phenylmethane)triisocyanate and isophorone diisocyanate,
and ketoxime-blocked products thereof or isocyanates of phenol-blocked
products; epoxy compounds such as ethylene glycol diglycidyl ether,
polyethylene glycol diglycidyl ether, glycerin di- or triglicydyl ether,
1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether,
diglicidyl aniline and diglycidyl amine; monoaldehydes such as
formaldehyde, acetaldehyde, propionaldehyde and butylaldehyde;
dialdehydes such as glyoxal, malonaldehyde, succindialdehyde,
glutardialdehyde, maleic dialdehyde and phthaldialdehyde;
amino-formaldehyde resins such as condensates with formaldehyde of
methylolurea, methylolmelamine, alkylated methylolurea, alkylated
methylolmelamine, acetoguanamine and benzoguanamine; salts of divalent
metals or trivalent metals such as sodium, potassium, magnesium, calcium,
aluminum, iron and nickel, and oxides of the metals. In particular,
amino-formaldehyde resins and dialdehydes are preferred.
Amino-formaldehyde resins preferably include methylol group-containing
compounds, and dialdehydes preferably include glyoxal. Methylolmelamine,
a methylol group-containing compound, is particularly preferred. The
crosslinking agent to be used may be a coupling agent such as a silane
coupling agent and a titanium coupling agent.

[0035]While the amount of the crosslinking agent to be blended may be
appropriately determined depending on the type of the polyvinyl
alcohol-based resin and the like, it is generally from about 1 to about
60 parts by weight, preferably from about 10 to about 55 parts by weight,
more preferably from 20 to 50 parts by weight, based on 100 parts by
weight of the polyvinyl alcohol-based resin. In such ranges, good
adhesion properties can be obtained.

[0036]In order to increase durability, a polyvinyl alcohol-based resin
having an acetoacetyl group is used. Also in this case, the crosslinking
agent may be used in an amount of about 1 to about 60 parts by weight,
preferably in an amount of about 10 to about 55 parts by weight, more
preferably in an amount of 20 to 50 parts by weight, similarly to the
above, based on 100 parts by weight of the polyvinyl alcohol-based resin.
If the amount of the crosslinking agent to be blended is too large, the
reaction of the crosslinking agent can proceed within a short time so
that the adhesive can tend to form a gel, and as a result, the adhesive
can have an extremely short pot life and thus can be difficult to use
industrially. From these points of view, the crosslinking agent is used
in the above amount, but the resin solution according to the present
invention can be stably used even when the amount of the crosslinking
agent is large as mentioned above, because the resin solution contains
the leveling agent containing an acetylene skeleton-containing compound.

[0037]The leveling agent used in the present invention contains an
acetylene skeleton-containing compound. Examples of the acetylene
skeleton-containing compound include acetylenic alcohols and acetylene
glycols. Acetylenic alcohols or acetylene glycols may be obtained by
reactions of acetylene with ketones or aldehydes. Examples of the
acetylene skeleton-containing compound also include derivatives such as
ethylene oxide and/or propylene oxide adducts of acetylene alcohols,
ethylene oxide and/or propylene oxide adducts of acetylene glycols, and
ether-modified acetylene alcohols or glycols such as ally ether-modified
acetylenic alcohols or glycols. In particular, ethylene oxide and/or
propylene oxide adducts of acetylene glycols are preferred. One or more
of acetylenic alcohols, acetylene glycols and derivatives thereof may be
used alone or in any combination or two or more kinds thereof as the
acetylenic skeleton-containing compound.

[0038]Examples of acetylene glycols and derivatives thereof include the
compounds represented by the following general formula (1) below. The
compounds have a symmetric structure composed of hydrophilic
moiety-hydrophobic moiety-hydrophilic moiety and are suitable as wetting
agents or penetrating agents and capable of reducing dynamic surface
tension or dynamic contact angle. The compounds also have a high level of
deforming or degassing properties and are easily dispersible in water.

##STR00001##

[0039]In the formula, R11 and R14 each represent a hydrogen atom
or a methyl group, R12 and R15 each represent a straight or
branched chain alkyl group of 1 to 8 carbon atoms, and R13 and
R16 each represent a hydrogen atom, an allyl group or an ethylene
oxide adduct moiety and/or a propylene oxide adduct moiety. The adduct
moiety may be represented by the formula --(AO)n-AOH, wherein n is
an integer of 1 to 7, preferably of 1 to 5, more preferably of 1 to 3,
and A represents an ethylene group and/or a propylene group.

[0040]In the acetylene glycols or derivatives thereof represented by
formula (1), R11 and R14 each preferably represent a methyl
group, and R12 and R15 each preferably represent an alkyl group
of 3 to 5 carbon atoms, particularly preferably a branched chain alkyl
group of 3 to 5 carbon atoms. In particular, the branched chain alkyl
group is preferably an isoalkyl group. R13 and R16 each
preferably represent an ethylene oxide adduct moiety and/or a propylene
oxide adduct moiety, particularly preferably an ethylene oxide adduct
moiety. Examples of the acetylene glycols represented by formula (1)
(wherein R13 and R16 each represent a hydrogen atom) include
2,5,8,11-tetramethyl-6-dodecine-5,8-diol,
2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol.

[0041]In an embodiment of the present invention, the leveling agent used
is generally an aqueous dispersion or solution of the acetylene
skeleton-containing compound. The concentration of the acetylene
skeleton-containing compound in the aqueous dispersion or solution is
generally, but not limited to, from 10 to 80% by weight, preferably from
20 to 70% by weight, more preferably from 30 to 50% by weight. Water may
be used as a dispersion medium for the aqueous dispersion or solution.
Besides water, alcohols such as methanol, ethanol and isopropanol,
alkylene glycols such as propylene glycol, glycol monoethers, or other
dispersion media may also be used. Any mixture of these dispersion media
may also be used. When ethylene oxide and/or propylene oxide adducts of
acetylene glycols are used as the acetylene skeleton-containing
compounds, certain dispersion media other than water are preferably used
so that wettability can be improved. In this case, such media other than
water are preferably alkylene glycols, and propylene glycol is
particularly preferred.

[0042]The leveling agent containing the acetylene skeleton-containing
compound is added in an amount of 0.01 to 10 parts by weight (in terms of
solid content), based on 100 parts by weight of the polyvinyl
alcohol-based resin. When the content of the leveling agent containing
the acetylene skeleton-containing compound is within the above range, the
wettability to transparent protective films can be ensured and polarizing
plates with satisfactory high-temperature water resistance and optical
properties can be produced. The content of the leveling agent containing
the acetylene skeleton-containing compound is preferably from 0.05 to 5
parts by weight, more preferably from 0.3 to 4 parts by weight, even more
preferably from 0.4 to 1 part by weight. If the content of the leveling
agent containing the acetylene skeleton-containing compound is more than
10 parts by weight, based on 100 parts by weight of the polyvinyl
alcohol-based resin, polarizing plates with satisfactory high-temperature
water resistance and optical properties cannot be produced. If the
content of the leveling agent containing the acetylene
skeleton-containing compound is less than 0.01 parts by weight, based on
100 parts by weight of the polyvinyl alcohol-based resin, wettability can
be insufficient, or it can be difficult to prevent polarizing plates from
suffering from unevenness in the process of preparing the polarizing
plates by precoating methods.

[0043]The adhesive for polarizing plate of the present invention is a
resin solution including the polyvinyl alcohol-based resin, the
crosslinking agent and the leveling agent containing an acetylene
skeleton-containing compound and generally used in the form of an aqueous
solution. While the resin solution may have any concentration, it
preferably has a concentration of 0.1 to 5% by weight, more preferably of
0.5 to 2% by weight, further more preferably of 1 to 1.5% by weight in
view of coatability, shelf stability and the like. If the content is less
than 0.1% by weight, sufficient adhesive strength may not be obtained. If
the content is more than 5% by weight, the pot life may be reduced.

[0044]The resin solution for use as the adhesive for polarizing plate may
be prepared by any method. In general, the resin solution may be prepared
by a process that includes mixing the polyvinyl alcohol-based resin and
the crosslinking agent, appropriately adjusting the concentration
thereof, and then adding the leveling agent containing an acetylene
skeleton-containing compound to the mixture. Optionally, a polyvinyl
alcohol-based resin having an acetoacetyl group may be used as the
polyvinyl alcohol-based resin. When the crosslinking agent is added in a
relatively large amount, the stability of the solution may be taken into
account, and therefore the mixing of the polyvinyl alcohol-based resin
and the leveling agent containing an acetylene skeleton-containing
compound may be followed by the addition of the crosslinking agent in
consideration of the timing of using the resulting resin solution and so
on. The concentration of the resin solution for use as the adhesive for
polarizing plate may be adjusted as appropriate, after the resin solution
is prepared.

[0045]The adhesive for polarizing plate may also contain various types of
tackifiers, stabilizing agents such as ultraviolet absorbing agents,
antioxidants, heat-resistant stabiizing agents, and hydrolysis-resistant
stabilizing agents, and so on. The adhesive for polarizing plate of the
present invention may also contain metal compound filler.

[0046]A polarizing plate of the present invention is manufactured by
lamination to bond a transparent protective film to a polarizer with the
adhesive. In the obtained polarizing plate, a transparent protective film
or transparent protective films are provided on one surface or both
surfaces of a polarizer with an adhesive agent layer formed with the
adhesive for polarizing plate interposed therebetween.

[0047]Coating of the adhesive may be performed on one/or both of the
transparent protective film and the polarizer. Coating of the adhesive is
preferably conducted so as to achieve a thickness after drying of the
order in the range of from 10 to 300 nm. The thickness of the adhesive
layer is more preferably from 10 to 250 nm, still more preferably from 20
to 200 nm, in terms of achieving uniform in-plane thickness and
sufficient adhesive force.

[0048]Examples of methods for controlling the thickness of the adhesive
layer include, but are not limited to, methods including controlling the
solid concentration of the adhesive solution or controlling an adhesive
coater. While the thickness of the adhesive layer may be measured by any
method, cross-sectional observation measurement by SEM (Scanning Electron
Microscopy) or TEM (Transmission Electron Microscopy) is preferably used.
The adhesive may be applied by any process, and various methods such as
roll methods, spraying methods, and immersion methods may be used for the
application.

[0049]The manufacturing method of the present invention is preferably
applied to precoating methods. Among precoating methods for manufacturing
polarizing plates, a certain method that includes applying the adhesive
for polarizing plate to a transparent protective film, subjecting the
adhesive to a drying process to form a dried pressure-sensitive adhesive
layer, and then laminating the pressure-sensitive adhesive layer to a
polarizer is preferably used so that production efficiency can be
improved. When conventional precoating methods are used, unevenness is
observed in the resulting polarizing plates, because adhesives have poor
wettability. In contrast, with the adhesive of the present invention,
polarizing plates can be prevented from suffering from unevenness, even
when produced by precoating methods.

[0050]For example, a precoating method may include applying the adhesive
for polarizing plate in the form of a solution to a polarizer and/or a
transparent protective film, laminating the polarizer and the transparent
protective film, and then subjecting the laminate to a drying process to
form a dried adhesive layer so that a polarizing plate can be obtained.
After the application of the adhesive, the polarizer and the transparent
protective film may be laminated using a roll laminator or the like.
After the lamination, the drying process may be performed at a drying
temperature of about 5 to about 150° C., preferably of 30 to
120° C., for a time period of 120 seconds or more, preferably of
300 seconds or more.

[0051]For example, another precoating method may include applying the
adhesive for polarizing plate to a transparent protective film, then
drying the adhesive to form a dried adhesive layer on the transparent
protective film, and then laminating a polarizer to the adhesive
layer-carrying transparent protective film through the adhesive layer so
that a polarizing plate can be obtained. The laminating may be performed
with a roll laminator or the like.

[0052]A polarizer is not limited especially but various kinds of polarizer
may be used. As a polarizer, for example, a film that is uniaxially
stretched after having dichromatic substances, such as iodine and
dichromatic dye, absorbed to hydrophilic high molecular weight polymer
films, such as polyvinyl alcohol type film, partially formalized
polyvinyl alcohol type film, and ethylene-vinyl acetate copolymer type
partially saponified film; poly-ene type orientation films, such as
dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride,
etc. may be mentioned. In these, a polyvinyl alcohol type film comprises
dichromatic materials such as iodine, dichromatic dye is suitably used.
Although thickness of polarizer is not especially limited, the thickness
of about 5 to about 80 μm is commonly adopted.

[0053]A polarizer that is uniaxially stretched after a polyvinyl alcohol
type film dyed with iodine is obtained by stretching a polyvinyl alcohol
film by 3 to 7 times the original length, after dipped and dyed in
aqueous solution of iodine. If needed the film may also be dipped in
aqueous solutions, such as boric acid and potassium iodide. Furthermore,
before dyeing, the polyvinyl alcohol type film may be dipped in water and
rinsed if needed. By rinsing polyvinyl alcohol type film with water,
effect of preventing un-uniformity, such as unevenness of dyeing, is
expected by making polyvinyl alcohol type film swelled in addition that
also soils and blocking inhibitors on the polyvinyl alcohol type film
surface may be washed off. Stretching may be applied after dyed with
iodine or may be applied concurrently, or conversely dyeing with iodine
may be applied after stretching. Stretching is applicable in aqueous
solutions, such as boric acid and potassium iodide, and in water bath.

[0054]Preferable Materials that form the transparent protective film,
which is provided one side or both sides of the polarizer is the material
having outstanding transparency, mechanical strength, heat stability and
outstanding moisture interception property, or the like. As materials of
the above-mentioned transparent protective film, for example, polyester
type polymers, such as polyethylene terephthalate and
polyethylenenaphthalate; cellulose type polymers, such as diacetyl
cellulose and triacetyl cellulose; acrylics type polymer, such as poly
methylmethacrylate; styrene type polymers, such as polystyrene and
acrylonitrile-styrene copolymer (AS resin); polycarbonate type polymer
may be mentioned. Besides, as examples of the polymer forming a
transparent protective film, polyolefin type polymers, such as
polyethylene, polypropylene, polyolefin that has cyclo- type or
norbornene structure, ethylene-propylene copolymer; vinyl chloride type
polymer; amide type polymers, such as nylon and aromatic polyamide; imide
type polymers; sulfone type polymers; polyether sulfone type polymers;
polyether-ether ketone type polymers; poly phenylene sulfide type
polymers; vinyl alcohol type polymer; vinylidene chloride type polymers;
vinyl butyral type polymers; arylate type polymers; polyoxymethylene type
polymers; epoxy type polymers; or blend polymers of the above-mentioned
polymers may be mentioned. The transparent protective film is generally
laminated to the polarizer with the adhesive layer, but thermosetting
resins or ultraviolet curing resins such as (meth)acrylic, urethane,
acrylic urethane, epoxy, or silicone resins may be used for the
transparent protective film. The transparent protective film may also
contain at least one type of any appropriate additive. Examples of the
additive include an ultraviolet absorbing agent, an antioxidant, a
lubricant, a plasticizer, a release agent, an anti-discoloration agent, a
flame retardant, a nucleating agent, an antistatic agent, a pigment, and
a colorant. The content of the thermoplastic resin in the transparent
protective film is preferably from 50 to 100% by weight, more preferably
from 50 to 99% by weight, still more preferably from 60 to 98% by weight,
particularly preferably from 70 to 97% by weight. If the content of the
thermoplastic resin in the transparent protective film is 50% by weight
or less, high transparency and other properties inherent in the
thermoplastic resin can fail to be sufficiently exhibited.

[0055]Moreover, as is described in JP-A No. 2001-343529 (WO 01/37007),
polymer films, for example, resin compositions including (A)
thermoplastic resins having substituted and/or non-substituted imido
group in sidechain, and (B) thermoplastic resins having substituted
and/or non-substituted phenyl and nitrile group in sidechain may be
mentioned. As an illustrative example, a film may be mentioned that is
made of a resin composition including alternating copolymer comprising
iso-butylene and N-methyl maleimide, and acrylonitrile-styrene copolymer.
A film comprising mixture extruded article of resin compositions etc. may
be used. Since the films are less in retardation and less in photoelastic
coefficient, faults such as unevenness due to a strain in a polarizing
plate can be removed and besides, since they are less in moisture
permeability, they are excellent in durability under humidified
environment.

[0056]Thickness of the transparent protective film can be properly
determined and generally in the range of from about 1 to about 500 μm
from the viewpoint of a strength, workability such as handlability,
requirement for a thin film and the like. Especially, the thickness is
preferably in the range of from 1 to 300 μm and more preferably in the
range of from 5 to 200 μm.

[0057]Note that in a case where the transparent protective films are
provided on both sides of a polarizer, the protective films made from the
same polymer may be used on both sides thereof or alternatively, the
protective films made from polymer materials different from each other
may also be used on respective both sides thereof.

[0058]At least one selected from a cellulose resin, a polycarbonate resin,
a cyclic polyolefin resin, and a (meth)acrylic resin is preferably used
for the transparent protective film according to the present invention.

[0059]The cellulose resin is an ester of cellulose and a fatty acid.
Examples of such a cellulose ester resin include triacetyl cellulose,
diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose, and
the like. In particular, triacetyl cellulose is preferred. Much
commercially available triacetyl celluloses are placing on sale and are
advantageous in view of easy availability and cost. Examples of
commercially available products of triacetyl cellulose include UV-50,
UV-80, SH-80, TD-80U, TD-TAC, and UZTAC (trade names) manufactured by
Fujifilm Corporation, and KC series manufactured by Konica Minolta. In
general, these triacetyl cellulose products have a thickness direction
retardation (Rth) of about 60 nm or less, while having an in-plane
retardation (Re) of almost zero.

[0060]Cellulose resin films with relatively small thickness direction
retardation may be obtained by processing any of the above cellulose
resins. Examples of the processing method include a method that includes
laminating a general cellulose-based film to a base film such as a
polyethylene terephthalate, polypropylene, or stainless steel film,
coated with a solvent such as cyclopentanone or methyl ethyl ketone,
drying the laminate by heating (for example, at 80 to 150° C. for
3 to 10 minutes) and then separating the base film; and a method that
includes coating a general cellulose resin film with a solution of a
norbornene resin, a (meth)acrylic resin or the like in a solvent such as
cyclopentanone or methyl ethyl ketone, drying the coated film by heating
(for example, at 80 to 150° C. for 3 to 10 minutes), and then
separating the coating.

[0061]The cellulose resin film with a relatively small thickness direction
retardation to be used may be a fatty acid cellulose resin film with a
controlled degree of fat substitution. While triacetyl cellulose for
general use has a degree of acetic acid substitution of about 2.8,
preferably, the degree of acetic acid substitution is controlled to 1.8
to 2.7, more preferably, so that the Rth can be reduced. The Rth may also
be controlled to be low by adding a plasticizer such as dibutyl
phthalate, p-toluenesulfonanilide, and acetyl triethyl citrate, to the
fatty acid-substituted cellulose resin. The plasticizer is preferably
added in amount of 40 parts by weight or less, more preferably of 1 to 20
parts by weight, still more preferably of 1 to 15 parts by weight, to 100
parts by weight of the fatty acid cellulose resin.

[0062]For example, the cyclic polyolefin resin is preferably a norbornene
resin. Cyclic olefin resin is a generic name for resins produced by
polymerization of cyclic olefin used as a polymerizable unit, and
examples thereof include the resins disclosed in JP-A Nos. 01-240517,
03-14882, and 03-122137. Specific examples thereof include ring-opened
(co)polymers of cyclic olefins, addition polymers of cyclic olefins,
copolymers (typically random copolymers) of cyclic olefins and
α-olefins such as ethylene and propylene, graft polymers produced
by modification thereof with unsaturated carboxylic acids or derivatives
thereof, and hydrides thereof. Examples of the cyclic olefin include
norbornene monomers.

[0064]The (meth)acrylic resin preferably has a glass transition
temperature (Tg) of 115° C. or more, more preferably of
120° C. or more, still more preferably of 125° C. or more,
particularly preferably of 130° C. or more. If the Tg is
115° C. or more, the resulting polarizing plate can have good
durability. The upper limit to the Tg of the (meth)acrylic resin is
preferably, but not limited to, 170° C. or less, in view of
formability and the like. The (meth)acrylic resin can form a film with an
in-plane retardation (Re) of almost zero and a thickness direction
retardation (Rth) of almost zero.

[0065]Any appropriate (meth)acrylic resin may be used as long as the
advantages of the present invention are not reduced. Examples of such a
(meth)acrylic resin include poly(meth)acrylate such as poly(methyl
methacrylate), methyl methacrylate-(meth)acrylic acid copolymers, methyl
methacrylate-(meth)acrylate copolymers, methyl
methacrylate-acrylate-(meth)acrylic acid copolymers, methyl
(meth)acrylate-styrene copolymers (such as MS resins), and alicyclic
hydrocarbon group-containing polymers (such as methyl
methacrylate-cyclohexyl methacrylate copolymers and methyl
methacrylate-norbornyl (meth)acrylate copolymers). Poly(C1-6 alkyl
(meth)acrylate) such as poly(methyl (meth)acrylate) is preferred, and a
methyl methacrylate-based resin mainly composed of a methyl methacrylate
unit (50 to 100% by weight, preferably 70 to 100% by weight) is more
preferred.

[0066]Examples of the (meth)acrylic resin include Acrypet VH and Acrypet
VRL20A each manufactured by Mitsubishi Rayon Co., Ltd., (meth)acrylic
resins having a ring structure in their molecule as disclosed in JP-A No.
2004-70296, and high-Tg (meth)acrylic resins produced by intramolecular
crosslinking or intramolecular cyclization reaction.

[0067]Lactone ring structure-containing (meth)acrylic resins may also be
used, because they have high heat resistance and high transparency and
also have high mechanical strength after biaxially stretched.

wherein R1, R2 and R3 each independently represent a
hydrogen atom or an organic residue of 1 to 20 carbon atoms. The organic
residue may contain an oxygen atom(s).

[0070]The content of the lactone ring structure represented by Formula (2)
in the lactone ring structure-containing (meth)acrylic resin is
preferably from 5 to 90% by weight, more preferably from 10 to 70% by
weight, still more preferably from 10 to 60% by weight, particularly
preferably from 10 to 50% by weight. If the content of the lactone ring
structure represented by Formula (2) in the lactone ring
structure-containing (meth)acrylic resin is less than 5% by weight, its
heat resistance, solvent resistance or surface hardness can be
insufficient. If the content of the lactone ring structure represented by
Formula (2) in the lactone ring structure-containing (meth)acrylic resin
is more than 90% by weight, its formability or workability can be poor.

[0071]The lactone ring structure-containing (meth)acrylic resin preferably
has a mass average molecular weight (also referred to as weight average
molecular weight) of 1,000 to 2,000,000, more preferably of 5,000 to
1,000,000, still more preferably of 10,000 to 500,000, particularly
preferably of 50,000 to 500,000. A mass average molecular weight outside
the above range is not preferred in view of formability or workability.

[0072]The lactone ring structure-containing (meth)acrylic resin preferably
has a Tg of 115° C. or more, more preferably of 120° C. or
more, still more preferably of 125° C. or more, particularly
preferably of 130° C. or more. For example, the resin with a Tg of
115° C. or more can produce good durability, when it is
incorporated in the form of a transparent protective film in a polarizing
plate. The upper limit to the Tg of the lactone ring structure-containing
(meth)acrylic resin is preferably, but not limited to, 170° C. or
less in view of formability and the like.

[0073]The total light transmittance of the lactone ring
structure-containing (meth)acrylic resin, which may be measured according
to ASTM-D-1003 with respect to injection molded products, is preferably
as high as possible, and specifically, it is preferably 85% or more, more
preferably 88% or more, still more preferably 90% or more. The total
light transmittance is an index of transparency, and a total light
transmittance of less than 85% can result in reduced transparency.

[0074]The transparent protective film to be used generally has an in-plane
retardation of less than 40 nm and a thickness direction retardation of
less than 80 nm. The in-plane retardation Re is expressed by the formula
Re=(nx-ny)×d, the thickness direction retardation Rth is expressed
by the formula Rth=(nx-nz)×d, and the Nz coefficient is represented
by the formula Nz=(nx-nz)/(nx-ny), where nx, ny and nz are the refractive
indices of the film in the directions of its slow axis, fast axis and
thickness, respectively, d is the thickness (nm) of the film, and the
direction of the slow axis is a direction in which the in-plane
refractive index of the film is maximum. Moreover, it is preferable that
the transparent protective film may have as little coloring as possible.
A protective film having a thickness direction retardation of from -90 nm
to +75 nm may be preferably used. Thus, coloring (optical coloring) of
polarizing plate resulting from a protective film may mostly be cancelled
using a protective film having a thickness direction retardation (Rth) of
from -90 nm to +75 nm. The thickness direction retardation (Rth) is
preferably from -80 nm to +60 nm, and especially preferably from -70 nm
to +45 nm.

[0075]Alternatively, the transparent protective film to be used may be a
retardation plate having an in-plane retardation of 40 nm or more and/or
a thickness direction retardation of 80 nm or more. The in-plane
retardation is generally controlled in the range of 40 to 200 nm, and the
thickness direction retardation is generally controlled in the range of
80 to 300 nm. The retardation plate for use as the transparent protective
film also has the function of the transparent protective film and thus
can contribute to a reduction in thickness.

[0076]Examples of the retardation plate include a birefringent film
produced by uniaxially or biaxially stretching a polymer material, an
oriented liquid crystal polymer film, and an oriented liquid crystal
polymer layer supported on a film. The thickness of the retardation plate
is generally, but not limited to, from about 20 to about 150 μm.

[0078]Examples of the liquid crystal polymer include various main-chain or
side-chain types having a liquid crystal molecular orientation
property-imparting conjugated linear atomic group (mesogen) introduced in
a main or side chain of a polymer. Examples of the main chain type liquid
crystal polymer include polymers having a mesogen group bonded thereto
via a flexibility-imparting spacer moiety, such as nematically ordered
polyester liquid-crystalline polymers, discotic polymers, and cholesteric
polymers. For example, the side-chain type liquid crystal polymer may be
a polymer comprising: a main chain skeleton of polysiloxane,
polyacrylate, polymethacrylate, or polymalonate; and a side chain having
a mesogen moiety that comprises a nematic orientation-imparting
para-substituted cyclic compound unit and is bonded thereto via a spacer
moiety comprising a conjugated atomic group. For example, any of these
liquid crystal polymers may be applied by a process that includes
spreading a solution of the liquid crystalline polymer on an alignment
surface such as a rubbed surface of a thin film of polyimide, polyvinyl
alcohol or the like, formed on the glass plate, and an obliquely
vapor-deposited silicon oxide surface, and heat-treating it.

[0079]The retardation plate may have any appropriate retardation depending
on the intended use such as compensation for coloration, viewing angle,
or the like due to the birefringence of various wave plates or liquid
crystal layers. Two or more types of retardation plates may also be
laminated to provide controlled optical properties, including
retardation.

[0080]A retardation plate satisfying the relation: nx=ny>nz,
nx>ny>nz, nx>ny=nz, nx>nz>ny, nz-nx>ny, nz>nx>ny,
or nz>nx=ny may be selected and used depending on various
applications. The relation ny-nz includes not only the case where ny is
completely equal to nz but also the case where ny is substantially equal
to nz.

[0081]For example, the retardation plate satisfying the relation
nx>ny>nz to be used preferably has a in-plane retardation of 40 to
100 nm, a thickness retardation of 100 to 320 nm, and an Nz coefficient
of 1.8 to 4.5. For example, the retardation plate satisfying the relation
nx>ny=nz (positive A plate) to be used preferably has a in-plane
retardation of 100 to 200 nm. For example, the retardation plate
satisfying the relation nz=nx>ny (negative A plate) to be used
preferably has a in-plane retardation of 100 to 200 nm. For example, the
retardation plate satisfying the relation nx>nz>ny to be used
preferably has a in-plane retardation of 150 to 300 nm and an Nz
coefficient of more than 0 and not more than 0.7. As described above, for
example, the retardation plate satisfying the relation nx=ny>nz,
nz>nx>ny or nz>nx=ny may also be used.

[0082]The transparent protective film may be appropriately selected
depending on the liquid crystal display to be produced therewith. In the
case of VA (Vertical Alignment, including MVA and PVA), it is preferred
that the transparent protective film on at least one side of the
polarizing plate (on the cell side) has a retardation. Specifically, it
preferably has a retardation Re in the range of 0 to 240 nm and a
retardation Rth in the range of 0 to 500 nm. In terms of
three-dimensional refractive index, the case of nx>ny=nz,
nx>ny>nz, nx>nz>ny, or nx=ny>nz (positive A-plate,
biaxial, negative C-plate) is preferred. In the case of VA, preferable is
a combination of the positive A-plate and the negative C-plate or single
use of the biaxial film. When polarizing plates are used on upper and
lower sides of a liquid crystal cell, the transparent protective films
may have a retardation on upper and lower sides of the liquid crystal
cell, or one of the upper and lower transparent protective films may has
a retardation.

[0083]For example, in the case of IPS (In-Plane Switching, including FFS),
the transparent protective film for use in one of the polarizing plates
may have or may not have a retardation. For example, a transparent
protective film with no retardation is preferably provided on both upper
and lower sides of a liquid crystal cell (cell sides), or otherwise a
transparent protective film with a retardation is preferably provided on
both or one of the upper and lower sides of a liquid crystal cell (for
example, the biaxial film satisfying relationship of nx>nz>ny on
the upper side with no retardation on the lower side or an positive
A-plate provided on the upper side with a positive C-plate provided on
the lower side). When it has a retardation, it preferably has a
retardation Re in the range of -500 to 500 nm and a retardation Rth in
the range of -500 to 500 nm. In terms of three-dimensional refractive
index, nx>ny=nz, nx>nz>ny, nz>nx=ny, or nz>nx>ny
(positive A-plate, biaxial, negative C-plate) is preferred.

[0084]The film with a retardation may be separately prepared and laminated
to a transparent protective film with no retardation so that the function
described above can be provided.

[0085]An easy adhesion treatment can be applied onto a surface of a
transparent protective film which is adhered to a polarizer. Examples of
easy adhesion treatments include: dry treatments such as a plasma
treatment and a corona treatment; chemical treatment such as alkaline
treatment (saponification); and a coating treatment in which an easy
adhesion layer is formed. Among them, preferable are a coating treatment
and an alkaline treatment each forming an easy adhesion layer. In
formation of an easy adhesion layer, there can be used each of various
kinds of easy adhesion materials such as a polyol resin, a polycarboxylic
resin and a polyester resin. Note that a thickness of an easy adhesion
layer is preferably usually from about 0.001 to about 10 μm, more
preferably from about 0.001 to about 5 μm and especially preferably
from about 0.001 to about 1 μm.

[0086]A hard coat layer may be prepared, or antireflection processing,
processing aiming at sticking prevention, diffusion or anti glare may be
performed onto the face on which the polarizing film of the above
described transparent protective film has not been adhered.

[0087]A hard coat processing is applied for the purpose of protecting the
surface of the polarizing plate from damage, and this hard coat film may
be formed by a method in which, for example, a curable coated film with
excellent hardness, slide property etc. is added on the surface of the
protective film using suitable ultraviolet curable type resins, such as
acrylic type and silicone type resins. Antireflection processing is
applied for the purpose of antireflection of outdoor daylight on the
surface of a polarizing plate and it may be prepared by forming an
antireflection film according to the conventional method etc. Besides, a
sticking prevention processing is applied for the purpose of adherence
prevention with adjoining layer.

[0088]In addition, an anti glare processing is applied in order to prevent
a disadvantage that outdoor daylight reflects on the surface of a
polarizing plate to disturb visual recognition of transmitting light
through the polarizing plate, and the processing may be applied, for
example, by giving a fine concavo-convex structure to a surface of the
protective film using, for example, a suitable method, such as rough
surfacing treatment method by sandblasting or embossing and a method of
combining transparent fine particle. As a fine particle combined in order
to form a fine concavo-convex structure on the above-mentioned surface,
transparent fine particles whose average particle size is 0.5 to 50
μm, for example, such as inorganic type fine particles that may have
conductivity comprising silica, alumina, titania, zirconia, tin oxides,
indium oxides, cadmium oxides, antimony oxides, etc., and organic type
fine particles comprising cross-linked of non-cross-linked polymers may
be used. When forming fine concavo-convex structure on the surface, the
amount of fine particle used is usually about 2 to 70 weight parts to the
transparent resin 100 weight parts that forms the fine concavo-convex
structure on the surface, and preferably 5 to 50 weight parts. An anti
glare layer may serve as a diffusion layer (viewing angle expanding
function etc.) for diffusing transmitting light through the polarizing
plate and expanding a viewing angle etc.

[0089]In addition, the above-mentioned antireflection layer, sticking
prevention layer, diffusion layer, anti glare layer, etc. may be built in
the protective film itself, and also they may be prepared as an optical
layer different from the protective film.

[0090]A polarizing plate of the present invention may be used in practical
use as an optical film laminated with other optical layers. Although
there is especially no limitation about the optical layers, one layer or
two layers or more of optical layers, which may be used for formation of
a liquid crystal display etc., such as a reflector, a transflective
plate, a retardation plate (a half wavelength plate and a quarter
wavelength plate included), and a viewing angle compensation film, may be
used. Especially preferable polarizing plates are; a reflection type
polarizing plate or a transflective type polarizing plate in which a
reflector or a transflective reflector is further laminated onto a
polarizing plate of the present invention; an elliptically polarizing
plate or a circular polarizing plate in which a retardation plate is
further laminated onto the polarizing plate; a wide viewing angle
polarizing plate in which a viewing angle compensation film is further
laminated onto the polarizing plate; or a polarizing plate in which a
brightness enhancement film is further laminated onto the polarizing
plate.

[0091]A reflective layer is prepared on a polarizing plate to give a
reflection type polarizing plate, and this type of plate is used for a
liquid crystal display in which an incident light from a view side
(display side) is reflected to give a display. This type of plate does
not require built-in light sources, such as a backlight, but has an
advantage that a liquid crystal display may easily be made thinner. A
reflection type polarizing plate may be formed using suitable methods,
such as a method in which a reflective layer of metal etc. is, if
required, attached to one side of a polarizing plate through a
transparent protective film etc.

[0092]As an example of a reflection type polarizing plate, a plate may be
mentioned on which, if required, a reflective layer is formed using a
method of attaching a foil and vapor deposition film of reflective
metals, such as aluminum, to one side of a matte treated protective film.
Moreover, a different type of plate with a fine concavo-convex structure
on the surface obtained by mixing fine particle into the above-mentioned
protective film, on which a reflective layer of concavo-convex structure
is prepared, may be mentioned. The reflective layer that has the
above-mentioned fine concavo-convex structure diffuses incident light by
random reflection to prevent directivity and glaring appearance, and has
an advantage of controlling unevenness of light and darkness etc.
Moreover, the protective film containing the fine particle has an
advantage that unevenness of light and darkness may be controlled more
effectively, as a result that an incident light and its reflected light
that is transmitted through the film are diffused. A reflective layer
with fine concavo-convex structure on the surface effected by a surface
fine concavo-convex structure of a protective film may be formed by a
method of attaching a metal to the surface of a transparent protective
film directly using, for example, suitable methods of a vacuum
evaporation method, such as a vacuum deposition method, an ion plating
method, and a sputtering method, and a plating method etc.

[0093]Instead of a method in which a reflection plate is directly given to
the protective film of the above-mentioned polarizing plate, a reflection
plate may also be used as a reflective sheet constituted by preparing a
reflective layer on the suitable film for the transparent film. In
addition, since a reflective layer is usually made of metal, it is
desirable that the reflective side is covered with a protective film or a
polarizing plate etc. when used, from a viewpoint of preventing
deterioration in reflectance by oxidation, of maintaining an initial
reflectance for a long period of time and of avoiding preparation of a
protective layer separately etc.

[0094]In addition, a transflective type polarizing plate may be obtained
by preparing the above-mentioned reflective layer as a transflective type
reflective layer, such as a half-mirror etc. that reflects and transmits
light. A transflective type polarizing plate is usually prepared in the
backside of a liquid crystal cell and it may form a liquid crystal
display unit of a type in which a picture is displayed by an incident
light reflected from a view side (display side) when used in a
comparatively well-lighted atmosphere. And this unit displays a picture,
in a comparatively dark atmosphere, using embedded type light sources,
such as a back light built in backside of a transflective type polarizing
plate. That is, the transflective type polarizing plate is useful to
obtain of a liquid crystal display of the type that saves energy of light
sources, such as a back light, in a well-lighted atmosphere, and can be
used with a built-in light source if needed in a comparatively dark
atmosphere etc.

[0095]A description of the elliptically polarizing plate or circularly
polarizing plate in which the retardation plate is laminated to the
polarizing plate will be made in the following paragraph. These
polarizing plates change linearly polarized light into elliptically
polarized light or circularly polarized light, elliptically polarized
light or circularly polarized light into linearly polarized light or
change the polarization direction of linearly polarization by a function
of the retardation plate. As a retardation plate that changes circularly
polarized light into linearly polarized light or linearly polarized light
into circularly polarized light, what is called a quarter wavelength
plate (also called λ/4 plate) is used. Usually, half-wavelength
plate (also called λ/2 plate) is used, when changing the
polarization direction of linearly polarized light.

[0096]Elliptically polarizing plate is effectively used to give a
monochrome display without above-mentioned coloring by compensating
(preventing) coloring (blue or yellow color) produced by birefringence of
a liquid crystal layer of a super twisted nematic (STN) type liquid
crystal display. Furthermore, a polarizing plate in which
three-dimensional refractive index is controlled may also preferably
compensate (prevent) coloring produced when a screen of a liquid crystal
display is viewed from an oblique direction. Circularly polarizing plate
is effectively used, for example, when adjusting a color tone of a
picture of a reflection type liquid crystal display that provides a
colored picture, and it also has function of antireflection. For example,
a retardation plate may be used that compensates coloring and viewing
angle, etc. caused by birefringence of various wavelength plates or
liquid crystal layers etc. Besides, optical characteristics, such as
retardation, may be controlled using laminated layer with two or more
sorts of retardation plates having suitable retardation value according
to each purpose. As retardation plates, birefringence films formed by
stretching films comprising suitable polymers, such as polycarbonates,
norbornene type resins, polyvinyl alcohols, polystyrenes, poly methyl
methacrylates, polypropylene; polyarylates and polyamides; aligned films
comprising liquid crystal materials, such as liquid crystal polymer; and
films on which an alignment layer of a liquid crystal material is
supported may be mentioned. A retardation plate may be a retardation
plate that has a proper retardation according to the purposes of use,
such as various kinds of wavelength plates and plates aiming at
compensation of coloring by birefringence of a liquid crystal layer and
of visual angle, etc., and may be a retardation plate in which two or
more sorts of retardation plates is laminated so that optical properties,
such as retardation, may be controlled.

[0097]The above-mentioned elliptically polarizing plate and an
above-mentioned reflected type elliptically polarizing plate are
laminated plate combining suitably a polarizing plate or a reflection
type polarizing plate with a retardation plate. This type of elliptically
polarizing plate etc. may be manufactured by combining a polarizing plate
(reflected type) and a retardation plate, and by laminating them one by
one separately in the manufacture process of a liquid crystal display. On
the other hand, the polarizing plate in which lamination was beforehand
carried out and was obtained as an optical film, such as an elliptically
polarizing plate, is excellent in a stable quality, a workability in
lamination etc., and has an advantage in improved manufacturing
efficiency of a liquid crystal display.

[0098]A viewing angle compensation film is a film for extending viewing
angle so that a picture may look comparatively clearly, even when it is
viewed from an oblique direction not from vertical direction to a screen.
As such a viewing angle compensation retardation plate, in addition, a
film having birefringence property that is processed by uniaxial
stretching or orthogonal biaxial stretching and a biaxial stretched film
as inclined alignment film etc. may be used. As inclined alignment film,
for example, a film obtained using a method in which a heat shrinking
film is adhered to a polymer film, and then the combined film is heated
and stretched or shrunk under a condition of being influenced by a
shrinking force, or a film that is aligned in oblique direction may be
mentioned. The viewing angle compensation film is suitably combined for
the purpose of prevention of coloring caused by change of visible angle
based on retardation by liquid crystal cell etc. and of expansion of
viewing angle with good visibility.

[0099]Besides, a compensation plate in which an optical anisotropy layer
consisting of an alignment layer of liquid crystal polymer, especially
consisting of an inclined alignment layer of discotic liquid crystal
polymer is supported with triacetyl cellulose film may preferably be used
from a viewpoint of attaining a wide viewing angle with good visibility.

[0100]The polarizing plate with which a polarizing plate and a brightness
enhancement film are adhered together is usually used being prepared in a
backside of a liquid crystal cell. A brightness enhancement film shows a
characteristic that reflects linearly polarized light with a
predetermined polarization axis, or circularly polarized light with a
predetermined direction, and that transmits other light, when natural
light by back lights of a liquid crystal display or by reflection from a
back-side etc., comes in. The polarizing plate, which is obtained by
laminating a brightness enhancement film to a polarizing plate, thus does
not transmit light without the predetermined polarization state and
reflects it, while obtaining transmitted light with the predetermined
polarization state by accepting a light from light sources, such as a
backlight. This polarizing plate makes the light reflected by the
brightness enhancement film further reversed through the reflective layer
prepared in the backside and forces the light re-enter into the
brightness enhancement film, and increases the quantity of the
transmitted light through the brightness enhancement film by transmitting
a part or all of the light as light with the predetermined polarization
state. The polarizing plate simultaneously supplies polarized light that
is difficult to be absorbed in a polarizer, and increases the quantity of
the light usable for a liquid crystal picture display etc., and as a
result luminosity may be improved. That is, in the case where the light
enters through a polarizer from backside of a liquid crystal cell by the
back light etc. without using a brightness enhancement film, most of the
light, with a polarization direction different from the polarization axis
of a polarizer, is absorbed by the polarizer, and does not transmit
through the polarizer. This means that although influenced with the
characteristics of the polarizer used, about 50 percent of light is
absorbed by the polarizer, the quantity of the light usable for a liquid
crystal picture display etc. decreases so much, and a resulting picture
displayed becomes dark. A brightness enhancement film does not enter the
light with the polarizing direction absorbed by the polarizer into the
polarizer but reflects the light once by the brightness enhancement film,
and further makes the light reversed through the reflective layer etc.
prepared in the backside to re-enter the light into the brightness
enhancement film. By this above-mentioned repeated operation, only when
the polarization direction of the light reflected and reversed between
the both becomes to have the polarization direction which may pass a
polarizer, the brightness enhancement film transmits the light to supply
it to the polarizer. As a result, the light from a backlight may be
efficiently used for the display of the picture of a liquid crystal
display to obtain a bright screen.

[0101]A diffusion plate may also be prepared between brightness
enhancement film and the above described reflective layer, etc. A
polarized light reflected by the brightness enhancement film goes to the
above described reflective layer etc., and the diffusion plate installed
diffuses passing light uniformly and changes the light state into
depolarization at the same time. That is, the diffusion plate returns
polarized light to natural light state. Steps are repeated where light,
in the unpolarized state, i.e., natural light state, reflects through
reflective layer and the like, and again goes into brightness enhancement
film through diffusion plate toward reflective layer and the like.
Diffusion plate that returns polarized light to the natural light state
is installed between brightness enhancement film and the above described
reflective layer, and the like, in this way, and thus a uniform and
bright screen may be provided while maintaining brightness of display
screen, and simultaneously controlling non-uniformity of brightness of
the display screen. By preparing such diffusion plate, it is considered
that number of repetition times of reflection of a first incident light
increases with sufficient degree to provide uniform and bright display
screen conjointly with diffusion function of the diffusion plate.

[0102]The suitable films are used as the above-mentioned brightness
enhancement film. Namely, multilayer thin film of a dielectric substance;
a laminated film that has the characteristics of transmitting a linearly
polarized light with a predetermined polarizing axis, and of reflecting
other light, such as the multilayer laminated film of the thin film
having a different refractive-index anisotropy; an aligned film of
cholesteric liquid-crystal polymer; a film that has the characteristics
of reflecting a circularly polarized light with either left-handed or
right-handed rotation and transmitting other light, such as a film on
which the aligned cholesteric liquid crystal layer is supported; etc. may
be mentioned.

[0103]Therefore, in the brightness enhancement film of a type that
transmits a linearly polarized light having the above-mentioned
predetermined polarization axis, by arranging the polarization axis of
the transmitted light and entering the light into a polarizing plate as
it is, the absorption loss by the polarizing plate is controlled and the
polarized light can be transmitted efficiently. On the other hand, in the
brightness enhancement film of a type that transmits a circularly
polarized light as a cholesteric liquid-crystal layer, the light may be
entered into a polarizer as it is, but it is desirable to enter the light
into a polarizer after changing the circularly polarized light to a
linearly polarized light through a retardation plate, taking control an
absorption loss into consideration. In addition, a circularly polarized
light is convertible into a linearly polarized light using a quarter
wavelength plate as the retardation plate.

[0104]A retardation plate that works as a quarter wavelength plate in a
wide wavelength ranges, such as a visible-light band, is obtained by a
method in which a retardation layer working as a quarter wavelength plate
to a pale color light with a wavelength of 550 nm is laminated with a
retardation layer having other retardation characteristics, such as a
retardation layer working as a half-wavelength plate. Therefore, the
retardation plate located between a polarizing plate and a brightness
enhancement film may consist of one or more retardation layers.

[0105]In addition, also in a cholesteric liquid-crystal layer, a layer
reflecting a circularly polarized light in a wide wavelength ranges, such
as a visible-light band, may be obtained by adopting a configuration
structure in which two or more layers with different reflective
wavelength are laminated together. Thus a transmitted circularly
polarized light in a wide wavelength range may be obtained using this
type of cholesteric liquid-crystal layer.

[0106]Moreover, the polarizing plate may consist of multi-layered film of
laminated layers of a polarizing plate and two of more of optical layers
as the above-mentioned separated type polarizing plate. Therefore, a
polarizing plate may be a reflection type elliptically polarizing plate
or a semi-transmission type elliptically polarizing plate, etc. in which
the above-mentioned reflection type polarizing plate or a transflective
type polarizing plate is combined with above described retardation plate
respectively.

[0107]Although an optical film with the above described optical layer
laminated to the polarizing plate may be formed by a method in which
laminating is separately carried out sequentially in manufacturing
process of a liquid crystal display etc., an optical film in a form of
being laminated beforehand has an outstanding advantage that it has
excellent stability in quality and assembly workability, etc., and thus
manufacturing processes ability of a liquid crystal display etc. may be
raised. Proper adhesion means, such as an adhesive layer, may be used for
laminating. On the occasion of adhesion of the above described polarizing
plate and other optical films, the optical axis may be set as a suitable
configuration angle according to the target retardation characteristics
etc.

[0108]In the polarizing plate mentioned above and the optical film in
which at least one layer of the polarizing plate is laminated, a
pressure-sensitive adhesive layer may also be prepared for adhesion with
other members, such as a liquid crystal cell etc. As pressure-sensitive
adhesive that forms pressure-sensitive layer is not especially limited,
and, for example, acrylic type polymers; silicone type polymers;
polyesters, polyurethanes, polyamides, polyethers; fluorine type and
rubber type polymers may be suitably selected as a base polymer.
Especially, a pressure-sensitive adhesive such as acrylics type
pressure-sensitive adhesives may be preferably used, which is excellent
in optical transparency, showing adhesion characteristics with moderate
wettability, cohesiveness and adhesive property and has outstanding
weather resistance, heat resistance, etc.

[0109]Moreover, a pressure-sensitive adhesive layer with low moisture
absorption and excellent heat resistance is desirable. This is because
those characteristics are required in order to prevent foaming and
peeling-off phenomena by moisture absorption, in order to prevent
decrease in optical characteristics and curvature of a liquid crystal
cell caused by thermal expansion difference etc. and in order to
manufacture a liquid crystal display excellent in durability with high
quality.

[0111]Proper method may be carried out to attach a pressure-sensitive
adhesive layer to one side or both sides of a polarizing film or an
optical film. As an example, about 10 to about 40 weight % of the
pressure-sensitive adhesive solution in which a base polymer or its
composition is dissolved or dispersed, for example, toluene or ethyl
acetate or a mixed solvent of these two solvents is prepared. A method in
which this solution is directly applied on a polarizing plate or an
optical film using suitable developing methods, such as flow method and
coating method, or a method in which a pressure-sensitive adhesive layer
is once formed on a separator, as mentioned above, and is then
transferred on a polarizing plate or an optical film may be mentioned.

[0112]A pressure-sensitive adhesive layer may also be prepared on one side
or both sides of a polarizing plate or an optical film as a layer in
which pressure-sensitive adhesives with different composition or
different kind etc. are laminated together. Moreover, when
pressure-sensitive adhesive layers are prepared on both sides,
pressure-sensitive adhesive layers that have different compositions,
different kinds or thickness, etc. may also be used on front side and
backside of a polarizing plate or an optical film. Thickness of a
pressure-sensitive adhesive layer may be suitably determined depending on
a purpose of usage or adhesive strength, etc., and generally is 1 to 500
μm, preferably to 200 μm, and more preferably 1 to 100 μm.

[0113]A temporary separator is attached to an exposed side of a
pressure-sensitive adhesive layer to prevent contamination etc., until it
is practically used. Thereby, it can be prevented that foreign matter
contacts pressure-sensitive adhesive layer in usual handling. As a
separator, without taking the above-mentioned thickness conditions into
consideration, for example, suitable conventional sheet materials that is
coated, if necessary, with release agents, such as silicone type, long
chain alkyl type, fluorine type release agents, and molybdenum sulfide
may be used. As a suitable sheet material, plastics films, rubber sheets,
papers, cloths, no woven fabrics, nets, foamed sheets and metallic foils
or laminated sheets thereof may be used.

[0114]In addition, in the present invention, ultraviolet absorbing
property may be given to the above-mentioned each layer, such as a
polarizer for a polarizing plate, a transparent protective film and an
optical film etc. and a pressure-sensitive adhesive layer, using a method
of adding UV absorbents, such as salicylic acid ester type compounds,
benzophenol type compounds, benzotriazol type compounds, cyano acrylate
type compounds, and nickel complex salt type compounds.

[0115]A polarizing plate or an optical film of the present invention may
be preferably used for manufacturing various equipment, such as liquid
crystal display, etc. Assembling of a liquid crystal display may be
carried out according to conventional methods. That is, a liquid crystal
display is generally manufactured by suitably assembling several parts
such as a liquid crystal cell, polarizing plates or optical films and, if
necessity, lighting system, and by incorporating driving circuit. In the
present invention, except that a polarizing plate or an optical film by
the present invention is used, there is especially no limitation to use
any conventional methods. Also any liquid crystal cell of arbitrary type,
such as TN type, and STN type, π type may be used.

[0116]Suitable liquid crystal displays, such as liquid crystal display
with which the above-mentioned polarizing plate or optical film has been
located at one side or both sides of the liquid crystal cell, and with
which a backlight or a reflector is used for a lighting system may be
manufactured. In this case, the polarizing plate or optical film by the
present invention may be installed in one side or both sides of the
liquid crystal cell. When installing the polarizing plate or optical
films in both sides, they may be of the same type or of different type.
Furthermore, in assembling a liquid crystal display, suitable parts, such
as diffusion plate, anti-glare layer, antireflection film, protective
plate, prism array, lens array sheet, optical diffusion plate, and
backlight, may be installed in suitable position in one layer or two or
more layers.

[0117]Subsequently, organic electro luminescence equipment (organic EL
display) will be explained. Generally, in organic EL display, a
transparent electrode, an organic emitting layer and a metal electrode
are laminated on a transparent substrate in an order configuring an
illuminant (organic electro luminescence illuminant). Here, an organic
emitting layer is a laminated material of various organic thin films, and
much compositions with various combination are known, for example, a
laminated material of hole injection layer comprising triphenylamine
derivatives etc., a luminescence layer comprising fluorescent organic
solids, such as anthracene; a laminated material of electronic injection
layer comprising such a luminescence layer and perylene derivatives,
etc.; laminated material of these hole injection layers, luminescence
layer, and electronic injection layer etc.

[0118]An organic EL display emits light based on a principle that positive
hole and electron are injected into an organic emitting layer by
impressing voltage between a transparent electrode and a metal electrode,
the energy produced by recombination of these positive holes and
electrons excites fluorescent substance, and subsequently light is
emitted when excited fluorescent substance returns to ground state. A
mechanism called recombination which takes place in a intermediate
process is the same as a mechanism in common diodes, and, as is expected,
there is a strong non-linear relationship between electric current and
luminescence strength accompanied by rectification nature to applied
voltage.

[0119]In an organic EL display, in order to take out luminescence in an
organic emitting layer, at least one electrode must be transparent. The
transparent electrode usually formed with transparent electric conductor,
such as indium tin oxide (ITO), is used as an anode. On the other hand,
in order to make electronic injection easier and to increase luminescence
efficiency, it is important that a substance with small work function is
used for cathode, and metal electrodes, such as Mg--Ag and Al--Li, are
usually used.

[0120]In organic EL display of such a configuration, an organic emitting
layer is formed by a very thin film about 10 nm in thickness. For this
reason, light is transmitted nearly completely through organic emitting
layer as through transparent electrode. Consequently, since the light
that enters, when light is not emitted, as incident light from a surface
of a transparent substrate and is transmitted through a transparent
electrode and an organic emitting layer and then is reflected by a metal
electrode, appears in front surface side of the transparent substrate
again, a display side of the organic EL display looks like mirror if
viewed from outside.

[0121]In an organic EL display containing an organic electro luminescence
illuminant equipped with a transparent electrode on a surface side of an
organic emitting layer that emits light by impression of voltage, and at
the same time equipped with a metal electrode on a back side of organic
emitting layer, a retardation plate may be installed between these
transparent electrodes and a polarizing plate, while preparing the
polarizing plate on the surface side of the transparent electrode.

[0122]Since the retardation plate and the polarizing plate have function
polarizing the light that has entered as incident light from outside and
has been reflected by the metal electrode, they have an effect of making
the mirror surface of metal electrode not visible from outside by the
polarization action. If a retardation plate is configured with a quarter
wavelength plate and the angle between the two polarization directions of
the polarizing plate and the retardation plate is adjusted to π/4, the
mirror surface of the metal electrode may be completely covered.

[0123]This means that only linearly polarized light component of the
external light that enters as incident light into this organic EL display
is transmitted with the work of polarizing plate. This linearly polarized
light generally gives an elliptically polarized light by the retardation
plate, and especially the retardation plate is a quarter wavelength
plate, and moreover when the angle between the two polarization
directions of the polarizing plate and the retardation plate is adjusted
to π/4, it gives a circularly polarized light.

[0124]This circularly polarized light is transmitted through the
transparent substrate, the transparent electrode and the organic thin
film, and is reflected by the metal electrode, and then is transmitted
through the organic thin film, the transparent electrode and the
transparent substrate again, and is turned into a linearly polarized
light again with the retardation plate. And since this linearly polarized
light lies at right angles to the polarization direction of the
polarizing plate, it cannot be transmitted through the polarizing plate.
As the result, mirror surface of the metal electrode may be completely
covered.

EXAMPLES

[0125]Description will be given of a construction and effect of the
present invention with examples and the like showing them below. Note
that in the examples, part or parts and % are based on weight unless
otherwise specified.

Example 1

Polarizer

[0126]A 75 μm-thick polyvinyl alcohol film with an average degree of
polymerization of 2400 and a saponification degree of 99.9% by mole was
immersed and allowed to swell in warm water at 30° C. for 60
seconds. The film was then immersed in an aqueous solution of
iodine/potassium iodide (0.5/8 in weight ratio) at a concentration of
0.3%, while stretched to a stretch ratio of 3.5 times, so that the film
was dyed. The film was then stretched in an aqueous borate ester solution
at 65° C. such that the total stretch ratio reached 6 times. After
the stretching, the film was dried in an oven at 40° C. for 3
minutes, resulting in a polarizer.

Transparent Protective Films

[0127]A 40 μm-thick triacetylcellulose film was used as a first
transparent protective film. A 70 μm-thick biaxially-stretched
norbornene film (Zeonor manufactured by Zeon Corporation) was used as a
second transparent protective film.

Preparation of Adhesive

[0128]An aqueous solution with a solid content adjusted to 1% was prepared
by dissolving 100 parts of an acetoacetyl group-containing polyvinyl
alcohol-based resin (1,200 in average degree of polymerization, 98.5% by
mole in degree of saponification, 5% by mole in degree of
acetoacetylation), 35 parts of methylol melamine, and 0.15 parts of a
leveling agent containing an acetylene skeleton-containing compound
(Olfine EXP4123 (trade name) manufactured by Nissin Chemical Industry
Co., Ltd., 40% in solid content, containing a mixture of water/propylene
glycol=10/50 in weight ratio as a dispersion medium) in pure water at a
temperature of 30° C.

Preparation of Polarizing Plate

[0129]The adhesive was applied to one side of each of the first and second
transparent protective films so that the adhesive layer could have a
thickness of 100 nm after drying. The application of the adhesive was
performed 30 minutes after the preparation thereof at a temperature of
30° C. The adhesive-coated transparent protective films were then
dried at 90° C. for 1 minute so that two adhesive layer-carrying
transparent protective films were obtained. The two adhesive
layer-carrying transparent protective films were laminated to both sides
of the polarizer by means of a roller to form a polarizing plate.

Examples 2 to 4 and Comparative Examples 1 to 5

[0130]Adhesives were prepared using the process of Example 1, except that
the type of each component and the content of each component used were
changed as shown in Table 1. Polarizing plates were also prepared using
the resulting adhesives in the same manner as Example 1.

Example 5

[0131]A polarizing plate was prepared in the same manner as in Example 1,
except that a 40 μm-thick poly(methyl methacrylate) resin (Acrypet VH
manufactured by Mitsubishi Rayon Co., Ltd.) was used as the second
transparent protective film in place of the 70 μm-thick
biaxially-stretched norbornene film.

Evaluation

[0132]The polarizing plates obtained in Examples and Comparative Examples
were evaluated as described below.

Unevenness in Polarizing Plates

[0133]Whether or not unevenness was observed in the polarizing plate in
its original state obtained in each example was checked and evaluated
according to the following criteria. [0134].circle-w/dot.: No unevenness
was observed in the resulting polarizing plate even in a dark room, and
no defective image display occurred. [0135]◯: Unevenness was
observed in the resulting polarizing plate in a dark room, but no
defective image display occurred. [0136]×: Unevenness was observed
in the resulting polarizing plate, and image display was affected.

[0137]A surface profilometer (WYKO NT3300 available from Matsushita
Electric Industrial Co., Ltd.) was used to measure unevenness in the
polarizing plate. A case where a ring-like profile as shown in FIG. 1 was
visually observed may be evaluated as "×"

Adhesion in Hot Water

[0138]The polarizing plate was cut into sample pieces each 50 mm long in
the absorption axis direction of the polarizer and 25 mm long in the
direction perpendicular to the absorption axis. The sample piece was
immersed in hot water at 60° C., and time until separation or
peeling occurred at the edge of the sample piece was measured.

Optical Properties, Amount of Change in Transmittance

[0139]A sample 50 mm×25 mm in size was obtained by cutting a
widthwise center portion of the resulting polarizing plate in such a
manner that the long side of the sample made an angle of 45° with
the absorption axis of the polarizing plate. The single-piece
transmittance (%) of the sample was measured with an integrating sphere
type spectral transmittance meter (DOT-3C, manufactured by Murakami Color
Research Laboratory). The amount of change in single-piece transmittance
was determined as described below. All the polarizing plates had a
single-piece transmittance (T1) of 42.5% immediately after the
preparation. The single-piece transmittance (T2) of each polarizing plate
was then measured 500 hours after the preparation. T2/T1 was calculated
as the amount of change in single-piece transmittance. In Table 1,
".circle-w/dot." represents cases where the amount of change was ±3%,
"603 " cases where the amount of change was ±5%, and "×" cases
where the amount of change was ±10%.

[0141]Table 1 show that no unevenness was observed in the polarizing
plates obtained in the examples, although they were produced by a
precoating method. From Table 1, it is apparent that each of the
adhesives used in the examples was smoothly applied to each transparent
protective film and had good wettability to each transparent protective
film. It is also apparent that the polarizing plates obtained in the
examples exhibited a high level of water-resistant adhesion at high
temperature and had satisfactory optical properties.

Patent applications by Masashi Shinagawa, Ibaraki-Shi JP

Patent applications by Masayuki Satake, Ibaraki-Shi JP

Patent applications by NITTO DENKO CORPORATION

Patent applications in class Light polarization without any external input

Patent applications in all subclasses Light polarization without any external input